A soil expert says after 20 years of composting, Nova Scotians still do not get it right.

Lise Leblanc, a professional agrologist with LP Consulting, said green bins are being stuffed with non-organic material and municipalities have piles of compost building up that nobody wants.

"Foreign material. That is a big problem with compost," said Leblanc.

She said compost piles are becoming too contaminated with plastics, glass and other non-organic items. Compost facilities find just about everything in the bins.

"They'll say they found tires, underwear, clothes. One big problem is balls. Footballs, soccer balls, forks, plates," said Leblanc.

"Everything is in there because it's just convenient."

The result, Leblanc said, is it's difficult to move the compost even after the raw organics are processed in the plants. Farmers are unwilling to take it, even for free, because they're not sold on the quality.

"They're saying, 'I don't want to put plastics on my land,'" Leblanc said.

Compost is divided into two main categories.

Class A compost is the more pure variety, but even it still contains some plastics. Class A compost does not allow any foreign matter greater than three millimetres in size per half litre. Its use is unrestricted and can be used agriculturally or in your yard.

Class B compost is less pure. It can contain as much as 3 pieces of sharp glass per half litre.

Earlier this year, the town of Yarmouth dumped Class B compost over about two hectares of land near Lake George.

Neighbours said it was full of plastics and other garbage and looked more like landfill than compost. The town is now working on a plan to clean it up.

Leblanc said making compost 100 per cent free of plastic is virtually impossible.

"We don't have the technology to completely clean out the plastics. And we don't have the financial means to have enough people to handpick every little bit," she said.

The problem, said Paul Arnold, an engineering professor at Acadia University and an organic waste management consultant, is we overestimated the performance of our composting facilities when we started using them.

He said the piles of compost are growing outside the facilities because organics take too long to decompose inside.

In many cases, he said that same material is run through the plant a second time, making the system more inefficient than it's supposed to be.

Part of the problem is what's being thrown in our green bins.

"We have been somewhat complacent over the years," he said.

His solution: stiffer fines and more education.